Conventional skin care products and other external preparations contain resin particles to fix skin flaws (to conceal spots, freckles, pores, etc.) by means of light scattering effects and to improve spreadability upon their application to the skin, as well as for various other purposes. Resin particles are also blended with coating materials and light diffusion members to exploit light scattering effects for matting or light diffusing purposes.
The external preparations containing resin particles are in some cases required to have improved sweat and sebum absorbance so that they can render the skin smooth and silky when applied to the skin. Therefore, the resin particles used with external preparations desirably have some water and oil absorbance.
For example, Patent Document 1 discloses a spherical polymer having an average particle diameter of 1 μm to 50 μm and an apparent specific gravity of 1.0 or less, each particle including one, two, or more spherical hollow tiny spaces inside it. The spherical polymer has some water and oil absorbance: 100 g of the spherical polymer is capable of absorbing 89.5 ml to 110 ml of water and 57.8 ml to 82.3 ml of oil (oleic acid).
Patent Document 2 discloses spherical porous fine cellulose particles with an outer shell layer and a porous inner core having a porosity of 5% to 50%. The spherical porous fine cellulose particles have some water and oil absorbance: 100 g of the particles are capable of absorbing 170 ml of water and 70 ml of oil.
Patent Document 3 discloses spherical porous resin powder having particle diameters of 1 μm to 40 μm and an average particle diameter of 2 μm to 20 μm, the powder including, on the spherical surface, pores of various sizes with mode pore diameters ranging from 5 angstroms to 160 angstroms (0.5 nm to 16 nm). The powder has some water and oil absorbance: 100 g of the powder is capable of absorbing 74.6 ml to 78.2 ml of water and 81.4 ml to 87.6 ml of oil (oleic acid).
Patent Document 4 discloses hollow flattened fine polymer particles with a shell wall made of an organic macromolecular compound. The hollow fine polymer particles become spherical upon absorbing a liquid substance and have some water and oil absorbance.